Regarding the weapon request: after looking at Winchester, Marlin, and Henry lever action guns for a while, I'm pretty sure the artist simply made a mistake. Lever action shotguns do exist but none of them look like that. IMO this most closely resembles a Marlin Model 336. As far as I can tell, no other lever action has all of these distinct features:
Oval, not square shaped lever
Rear barrel band that covers both barrel and magazine
Rear barrel band has sling swivel studs
Buckhorn sight
Sight is in front (relative to muzzle) of front barrel band instead of vice versa
I'm always learning though, so I'd appreciate a second opinion here before I touch any of the tags.